A printer is conventionally used mainly as a means for preparing a large quantity of prints at high speed. As a matter of fact, in the printing field where printing plates must be prepared every time even small quantity orders are placed, the printing business becomes unprofitable, so it has required a printing technology called an on-demand printing system that can respond to such small quantity orders.
And, as an image forming technique for providing a small quantity of prints at high speed and low price, image formation by an electrophotographic system is noticed. Among image forming apparatuses of an electrophotographic system, a wet image forming apparatus using a liquid developer with toner particles dispersed in an insulating carrier liquid has advantages which cannot be realized by a dry image forming apparatus, and in recent years the value thereof has been reviewed. The main advantages of the wet image forming apparatus are to be able to use very fine toner particles, thereby realizing a high image quality, and obtain a quality feeling like print and to be able to fix toner on sheets of paper at a comparatively low temperature, thereby realizing energy conservation. Particularly, in recent years, in correspondence with increasing demands for high image quality, the average diameter of toner particles used is apt to be made smaller and smaller.
As a wet image forming apparatus, conventionally, an image forming apparatus for developing an electrostatic latent image on the surface of a latent image carrier with a liquid developer including toner particles and a carrier liquid, transferring a toner image formed by development on the surface of the latent image carrier to an image receiving material, thereby obtaining a final image is known. Further, an image forming apparatus for transferring primarily the toner image developed by the liquid developer on the surface of the latent image carrier to an intermediate transfer member, furthermore transferring secondarily the toner image transferred to the surface of the intermediate transfer member to an image receiving material, thereby obtaining a final image is known.
In such an image forming apparatus, a cleaning apparatus, after image formation, for removing a liquid developer remaining on the surfaces of the latent image carrier, which is an image carrier, and the intermediate transfer member is installed. In the cleaning apparatus, conventionally, a cleaning blade similar to that of the dry image forming apparatus is used generally. However, when the average diameter of toner particles used is made smaller and becomes comparable in size to the ten-point average roughness Rz (JIS B 0633:2001) of the surface of the image carrier, toner particles thrust into concavities and pass through the cleaning blade, thus a problem arises that toner particles cannot be removed sufficiently. Particularly, if Rz of the image carrier is increased due to repetition of image output, passing of toner particles through the cleaning blade becomes remarkable and it is hard to sufficiently remove toner particles. When removal of the liquid developer is insufficient like this, in the next output image, a defective image quality such as gray background occurs, thus resulting in a problem.
With the foregoing problem in view, a cleaning apparatus having a cleaning roller made of an elastic member installed in front of a cleaning blade is proposed (for example, refer to Laid-Open Japanese Patent Application Publication No. 2002-82537). This device rotates the cleaning roller made of an elastic member by pressurizing it to an image carrier, suspends toner adhered to the surface of the image carrier in a carrier liquid, and then removes the toner by the cleaning blade, so that compared with a cleaning apparatus having only a cleaning blade, the device improves the removing rate of liquid developer.
However, even if the aforementioned measure is taken, the following problem remains unsettled.
Toner particles entering fine concavities of the surfaces of the latent image carrier which is the image carrier and intermediate transfer member can be suspended once in the carrier liquid by the cleaning roller made of an elastic member, though when removing the toner particles by the cleaning blade, they enter again the concavities, so that the problem remains unsettled still that toner particles pass through the cleaning blade. Particularly, when the surface of the image carrier becomes rough due to wear and toner particles are apt to enter it, it is difficult to remove sufficiently toner particles.